While numerous scientific studies that show impairments in olfactory function often represent an early and sensitive indicator of Alzheimer's Disease (AD) when used in conjunction with other clinical measures, there are no tests of olfactory function cleared by the FDA for this purpose. Consequently, the major goal of this application is comprised of two different but closely related components: 1.) to validate the use of the OLFACT" Test Battery as a sensitive, early indicator of mild cognitive impairment (MCI)/AD;and 2.) to use this data to seek and obtain FDA clearance of the OLFACT" Test Battery for use as a diagnostic test in the assessment of AD. To achieve this goal two specific goals are proposed. The first is to demonstrate that impairments in olfactory function--as ascertained by the OLFACT" Test Battery--are predictive of change in cognitive function and incidence of MCI with conversion to AD. To accomplish this, the Test Battery will be used to measure olfactory function in two longitudinal cohorts in which over 1500 participants are being evaluated for the development of MCI and AD. One cohort is from the Rush University Medical College Memory and Aging Project, the second is from the Massachusetts Alzheimer's Disease Research Center. This data will then form the basis for a 510(k) application to the FDA for the OLFACT" Test Battery. The availability of an FDA-cleared test as a valid and early predictor of AD would be of immense value, not only in the diagnosis of AD, per se, but also in assessing the efficacy of potential drug therapies or other therapeutic interventions as well as the development of future biomarkers. PUBLIC HEALTH RELEVANCE: Alzheimer's disease (AD) is the leading cause of dementia in old age, with 4 to 5 million Americans currently affected, and sharp increases in those numbers are expected by mid-century with the aging of the U.S. population. Because of its devastating impact on cognition and other behaviors and its chronic course, the disease already poses substantial public health challenges, and these are likely to increase in the coming decades. Impairments in the sense of smell are one of the earliest indicators associated with the development of AD and FDA clearance of the OLFACT" Test Battery as a diagnostic test in the assessment of AD would provide both clinicians and researchers a powerful tool in the fight against this disease.